Behavioral responses of wild chimpanzees toward a juvenile that suddenly lost its animacy due to a fall accident

Abstract

Detailed observations of animal reactions to a collapsed individual in wild are rare but essential to debates about the perception of death by nonhuman animals, including chimpanzees. A male juvenile chimpanzee named Volta (VO), a member of the M group in the Mahale Mountains National Park, fell from a tall tree and was temporarily incapacitated, suffering a severe concussion and nasal bone fracture. However, VO showed signs of gradual recovery. We compared the behavior of other chimpanzees towards VO with the previous reports on the behavior towards collapsed or recently dead group members. We found that behaviors towards VO were similar to those observed towards collapsed or dead members. These included other-regarding behaviors and aggressive behaviors, and notably, licking of VO’s blood, which has not been previously reported. Adult males tended to be in close proximity to VO for longer periods than adult females. The social situation with adult males including alpha male, surrounding VO likely influenced the behavior of other individuals. Chimpanzees demonstrated the ability to infer the state of recovery of the injured individual, by closely approaching, directing various behaviors, and observing the reactions of the victim, and demonstrate tolerance and consideration towards the victim.